arch/arm64/kernel/signal.c

   1 /*
   2  * Based on arch/arm/kernel/signal.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/cache.h>
  21 #include <linux/compat.h>
  22 #include <linux/errno.h>
  23 #include <linux/kernel.h>
  24 #include <linux/signal.h>
  25 #include <linux/personality.h>
  26 #include <linux/freezer.h>
  27 #include <linux/stddef.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/sizes.h>
  30 #include <linux/string.h>
  31 #include <linux/tracehook.h>
  32 #include <linux/ratelimit.h>
  33 #include <linux/syscalls.h>
  34
  35 #include <asm/daifflags.h>
  36 #include <asm/debug-monitors.h>
  37 #include <asm/elf.h>
  38 #include <asm/cacheflush.h>
  39 #include <asm/ucontext.h>
  40 #include <asm/unistd.h>
  41 #include <asm/fpsimd.h>
  42 #include <asm/ptrace.h>
  43 #include <asm/signal32.h>
  44 #include <asm/traps.h>
  45 #include <asm/vdso.h>
  46
  47 /*
  48  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  49  */
  50 struct rt_sigframe {
  51         struct siginfo info;
  52         struct ucontext uc;
  53 };
  54
  55 struct frame_record {
  56         u64 fp;
  57         u64 lr;
  58 };
  59
  60 struct rt_sigframe_user_layout {
  61         struct rt_sigframe __user *sigframe;
  62         struct frame_record __user *next_frame;
  63
  64         unsigned long size;     /* size of allocated sigframe data */
  65         unsigned long limit;    /* largest allowed size */
  66
  67         unsigned long fpsimd_offset;
  68         unsigned long esr_offset;
  69         unsigned long sve_offset;
  70         unsigned long extra_offset;
  71         unsigned long end_offset;
  72 };
  73
  74 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
  75 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
  76 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
  77
  78 static void init_user_layout(struct rt_sigframe_user_layout *user)
  79 {
  80         const size_t reserved_size =
  81                 sizeof(user->sigframe->uc.uc_mcontext.__reserved);
  82
  83         memset(user, 0, sizeof(*user));
  84         user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
  85
  86         user->limit = user->size + reserved_size;
  87
  88         user->limit -= TERMINATOR_SIZE;
  89         user->limit -= EXTRA_CONTEXT_SIZE;
  90         /* Reserve space for extension and terminator ^ */
  91 }
  92
  93 static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
  94 {
  95         return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
  96 }
  97
  98 /*
  99  * Sanity limit on the approximate maximum size of signal frame we'll
 100  * try to generate.  Stack alignment padding and the frame record are
 101  * not taken into account.  This limit is not a guarantee and is
 102  * NOT ABI.
 103  */
 104 #define SIGFRAME_MAXSZ SZ_64K
 105
 106 static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
 107                             unsigned long *offset, size_t size, bool extend)
 108 {
 109         size_t padded_size = round_up(size, 16);
 110
 111         if (padded_size > user->limit - user->size &&
 112             !user->extra_offset &&
 113             extend) {
 114                 int ret;
 115
 116                 user->limit += EXTRA_CONTEXT_SIZE;
 117                 ret = __sigframe_alloc(user, &user->extra_offset,
 118                                        sizeof(struct extra_context), false);
 119                 if (ret) {
 120                         user->limit -= EXTRA_CONTEXT_SIZE;
 121                         return ret;
 122                 }
 123
 124                 /* Reserve space for the __reserved[] terminator */
 125                 user->size += TERMINATOR_SIZE;
 126
 127                 /*
 128                  * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
 129                  * the terminator:
 130                  */
 131                 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
 132         }
 133
 134         /* Still not enough space?  Bad luck! */
 135         if (padded_size > user->limit - user->size)
 136                 return -ENOMEM;
 137
 138         *offset = user->size;
 139         user->size += padded_size;
 140
 141         return 0;
 142 }
 143
 144 /*
 145  * Allocate space for an optional record of <size> bytes in the user
 146  * signal frame.  The offset from the signal frame base address to the
 147  * allocated block is assigned to *offset.
 148  */
 149 static int sigframe_alloc(struct rt_sigframe_user_layout *user,
 150                           unsigned long *offset, size_t size)
 151 {
 152         return __sigframe_alloc(user, offset, size, true);
 153 }
 154
 155 /* Allocate the null terminator record and prevent further allocations */
 156 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
 157 {
 158         int ret;
 159
 160         /* Un-reserve the space reserved for the terminator: */
 161         user->limit += TERMINATOR_SIZE;
 162
 163         ret = sigframe_alloc(user, &user->end_offset,
 164                              sizeof(struct _aarch64_ctx));
 165         if (ret)
 166                 return ret;
 167
 168         /* Prevent further allocation: */
 169         user->limit = user->size;
 170         return 0;
 171 }
 172
 173 static void __user *apply_user_offset(
 174         struct rt_sigframe_user_layout const *user, unsigned long offset)
 175 {
 176         char __user *base = (char __user *)user->sigframe;
 177
 178         return base + offset;
 179 }
 180
 181 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 182 {
 183         struct user_fpsimd_state const *fpsimd =
 184                 &current->thread.uw.fpsimd_state;
 185         int err;
 186
 187         /* copy the FP and status/control registers */
 188         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 189         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
 190         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
 191
 192         /* copy the magic/size information */
 193         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
 194         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
 195
 196         return err ? -EFAULT : 0;
 197 }
 198
 199 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
 200 {
 201         struct user_fpsimd_state fpsimd;
 202         __u32 magic, size;
 203         int err = 0;
 204
 205         /* check the magic/size information */
 206         __get_user_error(magic, &ctx->head.magic, err);
 207         __get_user_error(size, &ctx->head.size, err);
 208         if (err)
 209                 return -EFAULT;
 210         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
 211                 return -EINVAL;
 212
 213         /* copy the FP and status/control registers */
 214         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
 215                                sizeof(fpsimd.vregs));
 216         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
 217         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
 218
 219         clear_thread_flag(TIF_SVE);
 220
 221         /* load the hardware registers from the fpsimd_state structure */
 222         if (!err)
 223                 fpsimd_update_current_state(&fpsimd);
 224
 225         return err ? -EFAULT : 0;
 226 }
 227
 228
 229 struct user_ctxs {
 230         struct fpsimd_context __user *fpsimd;
 231         struct sve_context __user *sve;
 232 };
 233
 234 #ifdef CONFIG_ARM64_SVE
 235
 236 static int preserve_sve_context(struct sve_context __user *ctx)
 237 {
 238         int err = 0;
 239         u16 reserved[ARRAY_SIZE(ctx->__reserved)];
 240         unsigned int vl = current->thread.sve_vl;
 241         unsigned int vq = 0;
 242
 243         if (test_thread_flag(TIF_SVE))
 244                 vq = sve_vq_from_vl(vl);
 245
 246         memset(reserved, 0, sizeof(reserved));
 247
 248         __put_user_error(SVE_MAGIC, &ctx->head.magic, err);
 249         __put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
 250                          &ctx->head.size, err);
 251         __put_user_error(vl, &ctx->vl, err);
 252         BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 253         err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 254
 255         if (vq) {
 256                 /*
 257                  * This assumes that the SVE state has already been saved to
 258                  * the task struct by calling preserve_fpsimd_context().
 259                  */
 260                 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
 261                                       current->thread.sve_state,
 262                                       SVE_SIG_REGS_SIZE(vq));
 263         }
 264
 265         return err ? -EFAULT : 0;
 266 }
 267
 268 static int restore_sve_fpsimd_context(struct user_ctxs *user)
 269 {
 270         int err;
 271         unsigned int vq;
 272         struct user_fpsimd_state fpsimd;
 273         struct sve_context sve;
 274
 275         if (__copy_from_user(&sve, user->sve, sizeof(sve)))
 276                 return -EFAULT;
 277
 278         if (sve.vl != current->thread.sve_vl)
 279                 return -EINVAL;
 280
 281         if (sve.head.size <= sizeof(*user->sve)) {
 282                 clear_thread_flag(TIF_SVE);
 283                 goto fpsimd_only;
 284         }
 285
 286         vq = sve_vq_from_vl(sve.vl);
 287
 288         if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq))
 289                 return -EINVAL;
 290
 291         /*
 292          * Careful: we are about __copy_from_user() directly into
 293          * thread.sve_state with preemption enabled, so protection is
 294          * needed to prevent a racing context switch from writing stale
 295          * registers back over the new data.
 296          */
 297
 298         fpsimd_flush_task_state(current);
 299         /* From now, fpsimd_thread_switch() won't touch thread.sve_state */
 300
 301         sve_alloc(current);
 302         err = __copy_from_user(current->thread.sve_state,
 303                                (char __user const *)user->sve +
 304                                         SVE_SIG_REGS_OFFSET,
 305                                SVE_SIG_REGS_SIZE(vq));
 306         if (err)
 307                 return -EFAULT;
 308
 309         set_thread_flag(TIF_SVE);
 310
 311 fpsimd_only:
 312         /* copy the FP and status/control registers */
 313         /* restore_sigframe() already checked that user->fpsimd != NULL. */
 314         err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
 315                                sizeof(fpsimd.vregs));
 316         __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
 317         __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
 318
 319         /* load the hardware registers from the fpsimd_state structure */
 320         if (!err)
 321                 fpsimd_update_current_state(&fpsimd);
 322
 323         return err ? -EFAULT : 0;
 324 }
 325
 326 #else /* ! CONFIG_ARM64_SVE */
 327
 328 /* Turn any non-optimised out attempts to use these into a link error: */
 329 extern int preserve_sve_context(void __user *ctx);
 330 extern int restore_sve_fpsimd_context(struct user_ctxs *user);
 331
 332 #endif /* ! CONFIG_ARM64_SVE */
 333
 334
 335 static int parse_user_sigframe(struct user_ctxs *user,
 336                                struct rt_sigframe __user *sf)
 337 {
 338         struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 339         struct _aarch64_ctx __user *head;
 340         char __user *base = (char __user *)&sc->__reserved;
 341         size_t offset = 0;
 342         size_t limit = sizeof(sc->__reserved);
 343         bool have_extra_context = false;
 344         char const __user *const sfp = (char const __user *)sf;
 345
 346         user->fpsimd = NULL;
 347         user->sve = NULL;
 348
 349         if (!IS_ALIGNED((unsigned long)base, 16))
 350                 goto invalid;
 351
 352         while (1) {
 353                 int err = 0;
 354                 u32 magic, size;
 355                 char const __user *userp;
 356                 struct extra_context const __user *extra;
 357                 u64 extra_datap;
 358                 u32 extra_size;
 359                 struct _aarch64_ctx const __user *end;
 360                 u32 end_magic, end_size;
 361
 362                 if (limit - offset < sizeof(*head))
 363                         goto invalid;
 364
 365                 if (!IS_ALIGNED(offset, 16))
 366                         goto invalid;
 367
 368                 head = (struct _aarch64_ctx __user *)(base + offset);
 369                 __get_user_error(magic, &head->magic, err);
 370                 __get_user_error(size, &head->size, err);
 371                 if (err)
 372                         return err;
 373
 374                 if (limit - offset < size)
 375                         goto invalid;
 376
 377                 switch (magic) {
 378                 case 0:
 379                         if (size)
 380                                 goto invalid;
 381
 382                         goto done;
 383
 384                 case FPSIMD_MAGIC:
 385                         if (user->fpsimd)
 386                                 goto invalid;
 387
 388                         if (size < sizeof(*user->fpsimd))
 389                                 goto invalid;
 390
 391                         user->fpsimd = (struct fpsimd_context __user *)head;
 392                         break;
 393
 394                 case ESR_MAGIC:
 395                         /* ignore */
 396                         break;
 397
 398                 case SVE_MAGIC:
 399                         if (!system_supports_sve())
 400                                 goto invalid;
 401
 402                         if (user->sve)
 403                                 goto invalid;
 404
 405                         if (size < sizeof(*user->sve))
 406                                 goto invalid;
 407
 408                         user->sve = (struct sve_context __user *)head;
 409                         break;
 410
 411                 case EXTRA_MAGIC:
 412                         if (have_extra_context)
 413                                 goto invalid;
 414
 415                         if (size < sizeof(*extra))
 416                                 goto invalid;
 417
 418                         userp = (char const __user *)head;
 419
 420                         extra = (struct extra_context const __user *)userp;
 421                         userp += size;
 422
 423                         __get_user_error(extra_datap, &extra->datap, err);
 424                         __get_user_error(extra_size, &extra->size, err);
 425                         if (err)
 426                                 return err;
 427
 428                         /* Check for the dummy terminator in __reserved[]: */
 429
 430                         if (limit - offset - size < TERMINATOR_SIZE)
 431                                 goto invalid;
 432
 433                         end = (struct _aarch64_ctx const __user *)userp;
 434                         userp += TERMINATOR_SIZE;
 435
 436                         __get_user_error(end_magic, &end->magic, err);
 437                         __get_user_error(end_size, &end->size, err);
 438                         if (err)
 439                                 return err;
 440
 441                         if (end_magic || end_size)
 442                                 goto invalid;
 443
 444                         /* Prevent looping/repeated parsing of extra_context */
 445                         have_extra_context = true;
 446
 447                         base = (__force void __user *)extra_datap;
 448                         if (!IS_ALIGNED((unsigned long)base, 16))
 449                                 goto invalid;
 450
 451                         if (!IS_ALIGNED(extra_size, 16))
 452                                 goto invalid;
 453
 454                         if (base != userp)
 455                                 goto invalid;
 456
 457                         /* Reject "unreasonably large" frames: */
 458                         if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 459                                 goto invalid;
 460
 461                         /*
 462                          * Ignore trailing terminator in __reserved[]
 463                          * and start parsing extra data:
 464                          */
 465                         offset = 0;
 466                         limit = extra_size;
 467
 468                         if (!access_ok(base, limit))
 469                                 goto invalid;
 470
 471                         continue;
 472
 473                 default:
 474                         goto invalid;
 475                 }
 476
 477                 if (size < sizeof(*head))
 478                         goto invalid;
 479
 480                 if (limit - offset < size)
 481                         goto invalid;
 482
 483                 offset += size;
 484         }
 485
 486 done:
 487         return 0;
 488
 489 invalid:
 490         return -EINVAL;
 491 }
 492
 493 static int restore_sigframe(struct pt_regs *regs,
 494                             struct rt_sigframe __user *sf)
 495 {
 496         sigset_t set;
 497         int i, err;
 498         struct user_ctxs user;
 499
 500         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 501         if (err == 0)
 502                 set_current_blocked(&set);
 503
 504         for (i = 0; i < 31; i++)
 505                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 506                                  err);
 507         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 508         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 509         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 510
 511         /*
 512          * Avoid sys_rt_sigreturn() restarting.
 513          */
 514         forget_syscall(regs);
 515
 516         err |= !valid_user_regs(&regs->user_regs, current);
 517         if (err == 0)
 518                 err = parse_user_sigframe(&user, sf);
 519
 520         if (err == 0) {
 521                 if (!user.fpsimd)
 522                         return -EINVAL;
 523
 524                 if (user.sve) {
 525                         if (!system_supports_sve())
 526                                 return -EINVAL;
 527
 528                         err = restore_sve_fpsimd_context(&user);
 529                 } else {
 530                         err = restore_fpsimd_context(user.fpsimd);
 531                 }
 532         }
 533
 534         return err;
 535 }
 536
 537 SYSCALL_DEFINE0(rt_sigreturn)
 538 {
 539         struct pt_regs *regs = current_pt_regs();
 540         struct rt_sigframe __user *frame;
 541
 542         /* Always make any pending restarted system calls return -EINTR */
 543         current->restart_block.fn = do_no_restart_syscall;
 544
 545         /*
 546          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 547          * be word aligned here.
 548          */
 549         if (regs->sp & 15)
 550                 goto badframe;
 551
 552         frame = (struct rt_sigframe __user *)regs->sp;
 553
 554         if (!access_ok(frame, sizeof (*frame)))
 555                 goto badframe;
 556
 557         if (restore_sigframe(regs, frame))
 558                 goto badframe;
 559
 560         if (restore_altstack(&frame->uc.uc_stack))
 561                 goto badframe;
 562
 563         return regs->regs[0];
 564
 565 badframe:
 566         arm64_notify_segfault(regs->sp);
 567         return 0;
 568 }
 569
 570 /*
 571  * Determine the layout of optional records in the signal frame
 572  *
 573  * add_all: if true, lays out the biggest possible signal frame for
 574  *      this task; otherwise, generates a layout for the current state
 575  *      of the task.
 576  */
 577 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 578                                  bool add_all)
 579 {
 580         int err;
 581
 582         err = sigframe_alloc(user, &user->fpsimd_offset,
 583                              sizeof(struct fpsimd_context));
 584         if (err)
 585                 return err;
 586
 587         /* fault information, if valid */
 588         if (add_all || current->thread.fault_code) {
 589                 err = sigframe_alloc(user, &user->esr_offset,
 590                                      sizeof(struct esr_context));
 591                 if (err)
 592                         return err;
 593         }
 594
 595         if (system_supports_sve()) {
 596                 unsigned int vq = 0;
 597
 598                 if (add_all || test_thread_flag(TIF_SVE)) {
 599                         int vl = sve_max_vl;
 600
 601                         if (!add_all)
 602                                 vl = current->thread.sve_vl;
 603
 604                         vq = sve_vq_from_vl(vl);
 605                 }
 606
 607                 err = sigframe_alloc(user, &user->sve_offset,
 608                                      SVE_SIG_CONTEXT_SIZE(vq));
 609                 if (err)
 610                         return err;
 611         }
 612
 613         return sigframe_alloc_end(user);
 614 }
 615
 616 static int setup_sigframe(struct rt_sigframe_user_layout *user,
 617                           struct pt_regs *regs, sigset_t *set)
 618 {
 619         int i, err = 0;
 620         struct rt_sigframe __user *sf = user->sigframe;
 621
 622         /* set up the stack frame for unwinding */
 623         __put_user_error(regs->regs[29], &user->next_frame->fp, err);
 624         __put_user_error(regs->regs[30], &user->next_frame->lr, err);
 625
 626         for (i = 0; i < 31; i++)
 627                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 628                                  err);
 629         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 630         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 631         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 632
 633         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 634
 635         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 636
 637         if (err == 0) {
 638                 struct fpsimd_context __user *fpsimd_ctx =
 639                         apply_user_offset(user, user->fpsimd_offset);
 640                 err |= preserve_fpsimd_context(fpsimd_ctx);
 641         }
 642
 643         /* fault information, if valid */
 644         if (err == 0 && user->esr_offset) {
 645                 struct esr_context __user *esr_ctx =
 646                         apply_user_offset(user, user->esr_offset);
 647
 648                 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
 649                 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
 650                 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 651         }
 652
 653         /* Scalable Vector Extension state, if present */
 654         if (system_supports_sve() && err == 0 && user->sve_offset) {
 655                 struct sve_context __user *sve_ctx =
 656                         apply_user_offset(user, user->sve_offset);
 657                 err |= preserve_sve_context(sve_ctx);
 658         }
 659
 660         if (err == 0 && user->extra_offset) {
 661                 char __user *sfp = (char __user *)user->sigframe;
 662                 char __user *userp =
 663                         apply_user_offset(user, user->extra_offset);
 664
 665                 struct extra_context __user *extra;
 666                 struct _aarch64_ctx __user *end;
 667                 u64 extra_datap;
 668                 u32 extra_size;
 669
 670                 extra = (struct extra_context __user *)userp;
 671                 userp += EXTRA_CONTEXT_SIZE;
 672
 673                 end = (struct _aarch64_ctx __user *)userp;
 674                 userp += TERMINATOR_SIZE;
 675
 676                 /*
 677                  * extra_datap is just written to the signal frame.
 678                  * The value gets cast back to a void __user *
 679                  * during sigreturn.
 680                  */
 681                 extra_datap = (__force u64)userp;
 682                 extra_size = sfp + round_up(user->size, 16) - userp;
 683
 684                 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
 685                 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
 686                 __put_user_error(extra_datap, &extra->datap, err);
 687                 __put_user_error(extra_size, &extra->size, err);
 688
 689                 /* Add the terminator */
 690                 __put_user_error(0, &end->magic, err);
 691                 __put_user_error(0, &end->size, err);
 692         }
 693
 694         /* set the "end" magic */
 695         if (err == 0) {
 696                 struct _aarch64_ctx __user *end =
 697                         apply_user_offset(user, user->end_offset);
 698
 699                 __put_user_error(0, &end->magic, err);
 700                 __put_user_error(0, &end->size, err);
 701         }
 702
 703         return err;
 704 }
 705
 706 static int get_sigframe(struct rt_sigframe_user_layout *user,
 707                          struct ksignal *ksig, struct pt_regs *regs)
 708 {
 709         unsigned long sp, sp_top;
 710         int err;
 711
 712         init_user_layout(user);
 713         err = setup_sigframe_layout(user, false);
 714         if (err)
 715                 return err;
 716
 717         sp = sp_top = sigsp(regs->sp, ksig);
 718
 719         sp = round_down(sp - sizeof(struct frame_record), 16);
 720         user->next_frame = (struct frame_record __user *)sp;
 721
 722         sp = round_down(sp, 16) - sigframe_size(user);
 723         user->sigframe = (struct rt_sigframe __user *)sp;
 724
 725         /*
 726          * Check that we can actually write to the signal frame.
 727          */
 728         if (!access_ok(user->sigframe, sp_top - sp))
 729                 return -EFAULT;
 730
 731         return 0;
 732 }
 733
 734 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 735                          struct rt_sigframe_user_layout *user, int usig)
 736 {
 737         __sigrestore_t sigtramp;
 738
 739         regs->regs[0] = usig;
 740         regs->sp = (unsigned long)user->sigframe;
 741         regs->regs[29] = (unsigned long)&user->next_frame->fp;
 742         regs->pc = (unsigned long)ka->sa.sa_handler;
 743
 744         if (ka->sa.sa_flags & SA_RESTORER)
 745                 sigtramp = ka->sa.sa_restorer;
 746         else
 747                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 748
 749         regs->regs[30] = (unsigned long)sigtramp;
 750 }
 751
 752 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 753                           struct pt_regs *regs)
 754 {
 755         struct rt_sigframe_user_layout user;
 756         struct rt_sigframe __user *frame;
 757         int err = 0;
 758
 759         fpsimd_signal_preserve_current_state();
 760
 761         if (get_sigframe(&user, ksig, regs))
 762                 return 1;
 763
 764         frame = user.sigframe;
 765
 766         __put_user_error(0, &frame->uc.uc_flags, err);
 767         __put_user_error(NULL, &frame->uc.uc_link, err);
 768
 769         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 770         err |= setup_sigframe(&user, regs, set);
 771         if (err == 0) {
 772                 setup_return(regs, &ksig->ka, &user, usig);
 773                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 774                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 775                         regs->regs[1] = (unsigned long)&frame->info;
 776                         regs->regs[2] = (unsigned long)&frame->uc;
 777                 }
 778         }
 779
 780         return err;
 781 }
 782
 783 static void setup_restart_syscall(struct pt_regs *regs)
 784 {
 785         if (is_compat_task())
 786                 compat_setup_restart_syscall(regs);
 787         else
 788                 regs->regs[8] = __NR_restart_syscall;
 789 }
 790
 791 /*
 792  * OK, we're invoking a handler
 793  */
 794 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 795 {
 796         struct task_struct *tsk = current;
 797         sigset_t *oldset = sigmask_to_save();
 798         int usig = ksig->sig;
 799         int ret;
 800
 801         rseq_signal_deliver(ksig, regs);
 802
 803         /*
 804          * Set up the stack frame
 805          */
 806         if (is_compat_task()) {
 807                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 808                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 809                 else
 810                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 811         } else {
 812                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 813         }
 814
 815         /*
 816          * Check that the resulting registers are actually sane.
 817          */
 818         ret |= !valid_user_regs(&regs->user_regs, current);
 819
 820         /*
 821          * Fast forward the stepping logic so we step into the signal
 822          * handler.
 823          */
 824         if (!ret)
 825                 user_fastforward_single_step(tsk);
 826
 827         signal_setup_done(ret, ksig, 0);
 828 }
 829
 830 /*
 831  * Note that 'init' is a special process: it doesn't get signals it doesn't
 832  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 833  * mistake.
 834  *
 835  * Note that we go through the signals twice: once to check the signals that
 836  * the kernel can handle, and then we build all the user-level signal handling
 837  * stack-frames in one go after that.
 838  */
 839 static void do_signal(struct pt_regs *regs)
 840 {
 841         unsigned long continue_addr = 0, restart_addr = 0;
 842         int retval = 0;
 843         struct ksignal ksig;
 844         bool syscall = in_syscall(regs);
 845
 846         /*
 847          * If we were from a system call, check for system call restarting...
 848          */
 849         if (syscall) {
 850                 continue_addr = regs->pc;
 851                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 852                 retval = regs->regs[0];
 853
 854                 /*
 855                  * Avoid additional syscall restarting via ret_to_user.
 856                  */
 857                 forget_syscall(regs);
 858
 859                 /*
 860                  * Prepare for system call restart. We do this here so that a
 861                  * debugger will see the already changed PC.
 862                  */
 863                 switch (retval) {
 864                 case -ERESTARTNOHAND:
 865                 case -ERESTARTSYS:
 866                 case -ERESTARTNOINTR:
 867                 case -ERESTART_RESTARTBLOCK:
 868                         regs->regs[0] = regs->orig_x0;
 869                         regs->pc = restart_addr;
 870                         break;
 871                 }
 872         }
 873
 874         /*
 875          * Get the signal to deliver. When running under ptrace, at this point
 876          * the debugger may change all of our registers.
 877          */
 878         if (get_signal(&ksig)) {
 879                 /*
 880                  * Depending on the signal settings, we may need to revert the
 881                  * decision to restart the system call, but skip this if a
 882                  * debugger has chosen to restart at a different PC.
 883                  */
 884                 if (regs->pc == restart_addr &&
 885                     (retval == -ERESTARTNOHAND ||
 886                      retval == -ERESTART_RESTARTBLOCK ||
 887                      (retval == -ERESTARTSYS &&
 888                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 889                         regs->regs[0] = -EINTR;
 890                         regs->pc = continue_addr;
 891                 }
 892
 893                 handle_signal(&ksig, regs);
 894                 return;
 895         }
 896
 897         /*
 898          * Handle restarting a different system call. As above, if a debugger
 899          * has chosen to restart at a different PC, ignore the restart.
 900          */
 901         if (syscall && regs->pc == restart_addr) {
 902                 if (retval == -ERESTART_RESTARTBLOCK)
 903                         setup_restart_syscall(regs);
 904                 user_rewind_single_step(current);
 905         }
 906
 907         restore_saved_sigmask();
 908 }
 909
 910 asmlinkage void do_notify_resume(struct pt_regs *regs,
 911                                  unsigned long thread_flags)
 912 {
 913         /*
 914          * The assembly code enters us with IRQs off, but it hasn't
 915          * informed the tracing code of that for efficiency reasons.
 916          * Update the trace code with the current status.
 917          */
 918         trace_hardirqs_off();
 919
 920         do {
 921                 /* Check valid user FS if needed */
 922                 addr_limit_user_check();
 923
 924                 if (thread_flags & _TIF_NEED_RESCHED) {
 925                         /* Unmask Debug and SError for the next task */
 926                         local_daif_restore(DAIF_PROCCTX_NOIRQ);
 927
 928                         schedule();
 929                 } else {
 930                         local_daif_restore(DAIF_PROCCTX);
 931
 932                         if (thread_flags & _TIF_UPROBE)
 933                                 uprobe_notify_resume(regs);
 934
 935                         if (thread_flags & _TIF_SIGPENDING)
 936                                 do_signal(regs);
 937
 938                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 939                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 940                                 tracehook_notify_resume(regs);
 941                                 rseq_handle_notify_resume(NULL, regs);
 942                         }
 943
 944                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 945                                 fpsimd_restore_current_state();
 946                 }
 947
 948                 local_daif_mask();
 949                 thread_flags = READ_ONCE(current_thread_info()->flags);
 950         } while (thread_flags & _TIF_WORK_MASK);
 951 }
 952
 953 unsigned long __ro_after_init signal_minsigstksz;
 954
 955 /*
 956  * Determine the stack space required for guaranteed signal devliery.
 957  * This function is used to populate AT_MINSIGSTKSZ at process startup.
 958  * cpufeatures setup is assumed to be complete.
 959  */
 960 void __init minsigstksz_setup(void)
 961 {
 962         struct rt_sigframe_user_layout user;
 963
 964         init_user_layout(&user);
 965
 966         /*
 967          * If this fails, SIGFRAME_MAXSZ needs to be enlarged.  It won't
 968          * be big enough, but it's our best guess:
 969          */
 970         if (WARN_ON(setup_sigframe_layout(&user, true)))
 971                 return;
 972
 973         signal_minsigstksz = sigframe_size(&user) +
 974                 round_up(sizeof(struct frame_record), 16) +
 975                 16; /* max alignment padding */
 976 }